Apolar growth of Neurospora crassa leads to increased secretion of extracellular proteins

Abstract

SummaryProtein secretion in filamentous fungi has been shown to be restricted to actively growing hyphal tips. To determine whether an increase in the amount of growing surface area of a fungus can lead to an increase in the amount of protein secretion, we examined secretion in a temperature-sensitive Neurospora crassa mcb mutant that shows a loss of growth polarity when incubated at restrictive temperature. Incubation of the mcb mutant at restrictive temperature results in a three-to fivefold increase in the level of extracellular protein and a 20-fold increase in carboxymethyl cellulase activity relative to a wild-type strain. A mutation in the cr-1 gene has been shown previously to suppress the apolar growth phenotype of the mcb mutant, and we find that the level of extracellular protein produced by a mcb;cr-1 double mutant was reduced to that of the wild-type control. Immunolocalization of a secreted endoglucanase revealed that proteins are secreted mainly at hyphal tips in hyphae exhibiting polar growth and over the entire surface area of bulbous regions of hyphae that are produced after a shift of the mcb mutant to restrictive temperature. These results support the hypothesis that secretion of extracellular protein by a filamentous fungus can be significantly increased by mutations that alter growth polarity.

The Secretion Pathway in Filamentous Fungi: A Biotechnological View

“…Recent work has reinforced this hypothesis (Gordon et al, 2000a,b;Lee et al, 1998). Using the novel glucoamylase::green fluorescent fusion protein (GLA::GFP) as secretion reporter to study protein secretion in Aspergillus niger, Gordon et al (2000a,b) observed that GFP fluorescence was predominant at the hyphal apices and showed that this approach is a promising tool for further research in this field, as it allows in vivo monitoring of protein secretion.…”

“…The apical localization of protein secretion has led to the suggestion of employing morphological mutants displaying an increased apical surface, i.e., hyperbranching mutants, as "supersecretion" strains (Lee et al, 1998). Moreover, hyperbranching strains often grow as compact pellets, which results in low-viscosity cultures and has additional technical advantages in the fermentation process.…”

Qipgene inFusarium oxysporumis required for normal hyphae morphology and virulence

“…Therefore, in the Δ Qip mutant, the cessation of hyphal tip elongation generates a signal to form hyphal branches. Numerous mutants have a defect in hyphal tip growth and branching (Perkins et al 2000), including mutants in signalling pathways (Lee et al 1998), the cytoskeleton (Xiang and Morris 1999), subunit of the Vacuolar H + (Bowman et al 2000) and protein kinases (Wang et al 2011). This result suggests that the Qip gene, a component of the RNA-silencing pathway, was active in other pathways to regulate normal hyphal growth and development.…”

Macrophomina phaseolina, Cause of Stem Canker Disease in Pigeonpea: Physiological Response under Different Nitrogen Source

“…In MphP, maximum increase in ECP was obtained in urea might be due to the increase in hyphal tips per unit length of hypha or the failure of growth polarity (Fig. 5-8), that tends to increase the secretion of ECP in the growth medium (Lee et al, 1998). The cell lysis, weakened cell wall, or slow hyphal growth increased ECP in mcb mutant of Neurospora crasssa (Lee et al, 1998).…”

“…5-8), that tends to increase the secretion of ECP in the growth medium (Lee et al, 1998). The cell lysis, weakened cell wall, or slow hyphal growth increased ECP in mcb mutant of Neurospora crasssa (Lee et al, 1998).…”